International Agency for Research on Cancer (IARC) - Summaries & Evaluations

(Group 2B)

For definition of Groups, see Preamble Evaluation.

VOL.: 56 (1993) (p. 229)
CAS No.: 105650-23-5
Chem. Abstr. Name: 1-Methyl-6-phenyl-1H-imidazo[4,5-b]pyridin-2-amine

5. Summary of Data Reported and Evaluation

5.1 Exposure data

PhIP (2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) has been found in cooked meat and fish at concentrations of up to 70 ng/g. A few determinations indicated that the levels of PhIP were higher than those of IQ, MeIQ and MeIQx.

5.2 Human carcinogenicity data

No data directly relevant to an evaluation of the carcinogenicity to humans of PhIP were available. Studies on the consumption of cooked meat and fish are summarized in the monograph on IQ.

5.3 Animal carcinogenicity data

PhIP was tested for carcinogenicity in one experiment in mice and in two experiments in rats by oral administration in the diet. It increased the incidence of lymphomas in mice of each sex. In rats, it produced adenocarcinomas of the small and large intestine in males and mammary adenocarcinomas in females.

Intraperitoneal injection of PhIP to newborn male mice increased the incidence of hepatic adenomas.

A single intraperitoneal dose of PhIP after a two-thirds hepatectomy, followed by further modulating treatment, enhanced development of foci of altered hepatocytes in the livers of rats.

5.4 Other relevant data

PhIP formed DNA adducts in vivo in rats and monkeys. In rodent cells in vitro, it induced DNA damage, gene mutation and chromosomal anomalies. It induced DNA damage and mutation in bacteria.

PhIP can be metabolized by human microsomes isolated from liver and colon to a species that damages bacterial DNA.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of PhIP.

There is sufficient evidence in experimental animals for the carcinogenicity of PhIP.

Overall evaluation

PhIP (2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.

Last updated 08/21/1997

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